Spelling these words do not pose a problem for me.  However, some may have a hard time, which is understandable, considering that there are similar cases in other homonym pairs such as effect/affect, except/accept, and principle/principal.

People misspelling these two words drive me absolutely nuts. I was eating at a table in a supermarket today and there was this large chef statue with a board that read "No love is sincerer then the love of food". I was that close to changing to another table and the thought of making a smart-ass comment on that board has also crossed my mind.